1. Field of the Invention
The present invention relates to the recovery of bituminous products from tar sands, and more particularly, but not by way of limitation, to improved compositions for separating bituminous products from sand particles. In one aspect the present invention relates to improved acidic solvent compositions for use in the recovery of bituminous products from tar sands, and to a method for recovering such bituminous products.
2. Discussion of Prior Art
Tar sands are naturally occurring deposits which are generally constituted of bulk inorganic particles, such as siliceous sands, that are impregnated with a matrix of heavy petroleum or bitumen containing various types of hydrocarbons. Historically, the term "tar sand" has been applied to these deposits because of their similarity in appearance to asphaltic compositions, although they have also been described as oil sands and bituminous sands.
Tar sand deposits are found in significantly large reserves, such as the Athabasca tar sand deposits located near Ft. McMarray, Canada. Tar sand deposits are also found near Vernal, Green River and Sunnyside, Utah. These tar sand deposits contain significant reserves of potentially recoverable bituminous products. For example, it has been estimated that on the average one cubic yard of tar sands contains one barrel of bituminous product.
Various processes have heretofore been proposed for separating the bituminous products from tar sands by treatment with water, water/surfactant mixtures, solvents, heat, and combinations of the above. Generally, the prior art processes for separating bituminous materials from tar sands requires some form of crushing, grinding or otherwise mechanically comminuting the agglomerated tar sands to a finely divided state in order to obtain a more thorough exposure of the bituminous matrix material to the action of the recovery technique.
Grinding or crushing of the masses of tar sand is difficult and expensive because of the excessive equipment wear caused by the siliceous material which has a hardness greater than most components of the tar sand handling equipment. This is particularly important where the process requires that the tar sands be comminuted to relatively finely divided particles in order to increase exposure of the bituminous matrix to the recovery process.
A typical prior art process for the separation and recovery of bituminous products from tar sand is disclosed in U.S. Pat. No. 4,096,057 entitled "Apparatus and Method for Recovery of Bituminous Products from Tar Sands". The patent discloses a high shear environment in a liquid phase which causes the masses of tar sand to be rapidly reduced by attrition to sand particles and also rapidly strips the bituminous product from the finely divided detritus and sand resulting from this abradent action.
Solvents for the bituminous product in the method and apparatus of the beforementioned U.S. Pat. No. 4,096,057 include kerosene, gasoline, water/surfactant mixtures and mixtures of such liquids. Further, elevated temperatures in the liquid phase are employed to accelerate the attrition and stripping action by the liquid; and the liquid phase has a sufficient density to impart momentum to tar sand masses and provides a high shear environment.
In recent years a substantial effort has been made by the petroleum industry to develop new and improved solvent compositions and methods for the economical recovery of bituminous products from tar sands. It would be an advance in the art if a method for recovering the bituminous products from tar sands could be achieved using a solvent composition which did not require a high shear environment.